My home made diffuser

[Guitar Zero]

Originally Posted by pultech

These are neat!
Why couldn't you make something like this out of a medium density foam. It would be light and easy to work?

I'm guessing you could, but it needs to be a reflective surface. i don't know if the foam would absorb sound or not?????

[Nordenstam]

Originally Posted by pultech

Why couldn't you make something like this out of a medium density foam. It would be light and easy to work?

Styrofoam 2D diffusor

Edit: adding link to this post, which have a link to a good 2D diffuser calculator along with instructions on using it.

Edit3: this post is probably more useful than the one linked to above: BBC PRD Repetition--am I allowed?

[Coryphee]

What is the height for each board?

[Jimna]

Originally Posted by jeremycox

Today i started a project to build some quadratic residue diffusers.
Overall not a difficult project--even though i used only hand tools to build this first test product. It took around 10 hours and cost less than $8.

Anyone have any reason to believe these wont work? I plan on building 7 more for the back wall of my room (which is around 16 feet away from my monitors).





Any suggestions?
Jeremy Cox

hi was wonering if you could update the original post with some material used in text since the pics arent showing up. what are the actual diffusor made from? whats their name as i look in Homedepot. thanks

[Seditionary]

Originally Posted by Jimna

hi was wonering if you could update the original post with some material used in text since the pics arent showing up.

+2 pleaaaaseee.

[gsjim]

+3 for updated pics!

[kannon19]

+4 for updated pics.

[PaulP]

I'm not sure why the pictures aren't showing up but I dug their addresses out
of the page source and they still exist. Funny thing is that now that I've
looked at them they show up properly in the thread.

http://i22.photobucket.com/albums/b3...x/DSC02482.jpg

http://i22.photobucket.com/albums/b3...x/DSC02483.jpg

Edit: the above links may not work for some reason. The following
addresses are good if you remove the "x" in front and copy the
address into your location bar :

xhttp://i22.photobucket.com/albums/b307/dangercox/DSC02482.jpg
xhttp://i22.photobucket.com/albums/b307/dangercox/DSC02483.jpg

Edit2: Hmm, that only works if you copy the address to another browser.
There's definitely something going on behind the scenes !

One last try to import them as attachments :





If jeremycox would like me to stop screwing around with his pictures let
me know and I'll desist.

Paul P

[kannon19]

Originally Posted by PaulP

Funny thing is that now that I've
looked at them they show up properly in the thread.
Paul P

I believe that his account was not used for too long, but you going there reset some kind of timer on their website. So, thanks!

Those look nice, btw. thumbsup

[pkarpiozo]

Guys would that hugely matter if i will make skyline type using 4x6 cm pieces instead of 5x5cm ???

Thanks.

asking cause have loads of pieces in this dimensions in my place.

[Nordenstam]

It'll work fine! Place the smaller side of the rectangles in the direction you want most diffusion to occur, the array will diffuse to a higher frequency in that direction.

[Schaap]

Originally Posted by pkarpiozo

Guys would that hugely matter if i will make skyline type using 4x6 cm pieces instead of 5x5cm ???

Thanks.

asking cause have loads of pieces in this dimensions in my place.

What Lupo said; such a Skyline has some frequency direction. If it's finished can you take a photo? I wonder how it looks

[AnthonyRochester]

Originally Posted by Guitar Zero

The skyline diffusors are 2x2's cut to a specified length according to the pattern and gorilla glued to a thin piece of plywood. Each length is stained a different shade. They are HEAVY, and a little hard to get up on the wall, but I'm pleased the way they turned out. Here's the formula for the pieces of wood if you're interested: Next time, i think I'll try balsa wood.
PME Records QRD Diffusor Construction

for the skyline ones, is it really necessary to use a formula of specific lengths and use a designed pattern? Isn't it fine to just use random lengths and random pattern?

I am making one where the ends are cut on angles, as I have seen in some pictures..

[avare]

Originally Posted by beebay007

for the skyline ones, is it really necessary to use a formula of specific lengths and use a designed pattern?

Yes.

Isn't it fine to just use random lengths and random pattern?

No.


Well defined and patterned,
Andre

[vonrichter]

So has anyone come up with a plan for cost-effective diffusion for medium sized rooms that actually works yet? :-P

[aljaz]

HI there,

I made those Skyline diffusers from EPS material (8" height ) and diffusers with 15 residues (depth 10" and width 1" ).

[Hic&Nunc]

Hi there,

One question;

I'm about to design a 1D QRD diffuser for positioning behind me, Shell depth will be 8 inches while width will be 1,57 inches. I have the opportunity to whether construct a 37 panel order or 3 * 11 panel which would allow me to flip one according to the barker code.

What do you think I should do?

Thank you.

[aljaz]

Originally Posted by Hic&Nunc

Hi there,

One question;

I'm about to design a 1D QRD diffuser for positioning behind me, Shell depth will be 8 inches while width will be 1,57 inches. I have the opportunity to whether construct a 37 panel order or 3 * 11 panel which would allow me to flip one according to the barker code.

What do you think I should do?

Thank you.

First I need to know the dimensions of your room then I can give a proper advise. If you have some drawings available can be even better.

Feel free to contact me on pm.

[vonrichter]

Originally Posted by aljaz

HI there,

I made those Skyline diffusers from EPS material (8" height ) and diffusers with 15 residues (depth 10" and width 1" ).

Nice pics - can you post more details on construction/parts/plans total cost?

[collo]

Originally Posted by Hic&Nunc

Hi there,

One question;

I'm about to design a 1D QRD diffuser for positioning behind me, Shell depth will be 8 inches while width will be 1,57 inches. I have the opportunity to whether construct a 37 panel order or 3 * 11 panel which would allow me to flip one according to the barker code.

What do you think I should do?

Thank you.

Whilst the N37 would look nice, you do need some repeats to get correct diffusion, so the multiple N11's would technically be better

[aljaz]

Originally Posted by vonrichter

Nice pics - can you post more details on construction/parts/plans total cost?

Send me pm. For both items I made a patent invention.
Material costs: Sky line : 42 $
1 D diffuser : 250 $

[fitZ]

Maybe a 2d Diffractal would do the trick.

[PaulP]

Originally Posted by aljaz

For both items I made a patent invention.

You patented a styrofoam skyline ?

Paul P

[Lonely Raven]

Originally Posted by PaulP

You patented a styrofoam skyline ?

Paul P

You can submit a patent on anything...that doesn't mean it's going to be accepted as an original idea.

[PaulP]

Originally Posted by fitZ

Maybe a 2d Diffractal would do the trick.

That's beautiful. But it would take a lifetime to make.

Paul P

[johndykstra]

Originally Posted by aljaz

Send me pm. For both items I made a patent invention.
Material costs: Sky line : 42 $
1 D diffuser : 250 $

this is priceless

[thebjorno]

What lighter material could I use without compromising the diffusion (or budget, for that matter) of the skyline diffuser.? I don't know off hand what balsa would cost, or how well it would diffuse, but I do know that it's not that durable. Are there any other recommended materials that would help.

[Dange]

Originally Posted by Hic&Nunc

Hi there,

One question;

I'm about to design a 1D QRD diffuser for positioning behind me, Shell depth will be 8 inches while width will be 1,57 inches. I have the opportunity to whether construct a 37 panel order or 3 * 11 panel which would allow me to flip one according to the barker code.

What do you think I should do?

Thank you.

From Cox and D'Antonio, the ones flipped according to the barker sequence perform better than a single period (one QRD) and the repeated period (identical repeated QRD). I think that's using 5 N=7 QRDs though, sequence would be: normal, flipped, normal, normal, normal.

[Xenon]

The term "flipped" has caused much confusion.

Collo explained here how "flipping" (rotating a QRD panel 180 deg.) is not really going to do much -- instead consider an inverse or divergent prime number panel.

"Because the panels are basically symmetrical, your "flipped" [180 deg.] panel would give the same diffusion pattern - no use as the alternate panel in a Barker sequence." Look at the pics so see the difference between "flipped" as in rotated, and a proper inverse.

If you visit the QRDUDE software (free QRD design software by Collo) guide page here,and scroll down to the "Multiple panels" section, you find that as well as a proper inverse, panel modulation can be done. Scroll down just a bit more to the line "There are several possibilities for the modulating panel to be used:" with the examples and pics. See: Option #4: "Rotate a standard panel by 180 degrees. This is the simplest solution, although the change in diffusion angles is small compared to that obtained with the other approaches. The panel is equivalent to a standard panel that has been left-shifted one well..."

Note that:
"The modulation works best at multiples of the design frequency. Only at these frequencies do the diffuser and its inverse create exactly opposite pressures. At other frequencies, the modulation is likely to help with the scattering as it breaks up periodicity lobes, but in a more uncontrolled manner." (p. 251, Acoustic Absorbers and Diffusers: Theory, Design and Application By Trevor Cox, Peter D'Antonio).

Trevor replied here & here to a letter I wrote him on the question of sticking to the design frequency for modulation. Here is the Q&A:

Me: My question is a simple one. My N23 design freq. = 994Hz, Max Well Depth [MWD] = 135mm. With this arrangement: N23 N23 N19 N23 (Barker code: +1 +1 -1 +1) To make N19 design freq. 994Hz (max well depth 127mm) or disregard the design Hz, and just build to the same depth (135mm) as the N23? I ask, in that from reading it seems that matching the design Hz is preferable -- though some on the board disagree, stating that a mismatch is actually preferable, in terms of modulation. Could you clarify this point?

Trevor replies: Probably impossible to answer the question without a few predictions. But given you are using relatively large N primes, flat plate frequencies are not a worry, so choosing the same design frequency is OK (choosing a different one is probably OK as well!)

Due to the above, I altered my array for 4 N23 panels to this (matching MWD in the two different panels, and selecting iN23 instead of N19 for modulation):

Barker code
+1 = N23+0: design freq. = 994Hz = 135mm MWD
-1 = iN23+4: design freq. = 1055Hz = 135mm MWD

iN23(+4) is an inverse N23, shifted up 4 depth units (and left 9 wells), which allows maximum depth reduction (as possible) for the deepest well. The left shift allows the frame sides to be used as part of the furthest left- and right-side wells. I used QRDUDE to run my calculations.

Here is a picture of the array. The 2 rows of four panels measure 4 meters wide by 2 meters high on a 5 meter wide wall (1 panel's height = 94cm):



Absorption hasn't been installed yet. You can see the iN23+4 panels as they have the spacers in the middle of 4 consecutive deep wells (a couple spacers need yet to be affixed).

Collo wrote: "The iN23+4 is not the inverse of the N23+0 -- Having said that, you are maximising the "free ride" for both, thus getting the lowest design frequencies for each. Given Trevor's earlier comments downplaying the importance of having an exact inverse, this is should be as good as any other non-exact arrangement."

My conclusion, "This seems useful, in that now there are two decent modulation options beyond the iN23+0. I can use an N19, or the iN23+4. In terms of studio decor, the iN23+4 will look much better and cover a larger area." I hope this info is helpful.

If you wish to experience pain, read the thread of my own QRD thrashing (don't do it!) from here. Some pics of how the build went with XPS foam core construction are here. The term "flipping" as a primary solution for QRD modulation needs further discussion. I highly recommend QRDUDE and the accompanying explanatory pages -- a real lifesaver. Much thought and expertise has gone into its creation. My live room has benefited in a lively way from the N23/iN23 array.

Cheers, Xenon

PS These panels cost about $50. per in materials, including stain and finishing, in Japan (where all materials are more expensive than in N.Amer.). The top/bottom well inserts of hard rubber (the black areas) added about $8.00. So, call it $60. per panel. It did take some time.

Originally Posted by Dange

From Cox and D'Antonio, the ones flipped according to the barker sequence perform better than a single period (one QRD) and the repeated period (identical repeated QRD)....

[Ronnie LeBlanc]

Originally Posted by jeremycox

Today i started a project to build some quadratic residue diffusers.
Overall not a difficult project--even though i used only hand tools to build this first test product. It took around 10 hours and cost less than $8.

Anyone have any reason to believe these wont work? I plan on building 7 more for the back wall of my room (which is around 16 feet away from my monitors).





Any suggestions?
Jeremy Cox

Hey man! Those are killer!

I'm gonna try them also but was wondering if you knew if I'd be ok using some left over elaminated (spelling!!) flooring. I have a bunch left over. They are wood grain. And they are 7.5 inches wide X 4 feet long. They would look good as the caps for a diffuser. Do you think they would work well?

Good job by the way!

Ron